1. Field of the Invention
The present invention relates to the field of cosmetic surgery generally and specifically to liposuction and soft-tissue plastic surgery. More particularly, the invention relates to a device and method for measuring soft tissue thickness with a handheld apparatus utilizing ultrasound. This device can be easily employed to monitor changes in adipose tissue during a liposuction surgical procedure.
2. Description of Related Art
Liposuction, also known as liposculpture, lipoplasty or suction lipectomy, is a technique to remove stubborn fat deposits that won""t respond to dieting and exercise. Liposuction was introduced to the United States in the early 1980""s and has since grown in popularity. In a liposuction procedure, a very small incision is made in the skin and a cannula, i.e., a thin, smooth, hollow, blunt, surgical suction rod is inserted. The cannula is connected to a vacuum source with a suction tube and the fat is sucked out leaving the skin, muscle, nerves and blood vessels intact. This procedure allows the surgeon to sculpt and improve body contour with minimal pain and scaring. Through a liposuction procedure fat cells are permanently removed and since fat cells are not thought to regenerate, body contour improvement should be permanent Typically, the amount of fat to be removed is determined by the surgeon by feeling and pinching the skin throughout the surgical procedure. Even with a highly skilled surgeon, variations from the ideal results are possible. While complications are rare they can include uneven skin surface, bleeding, infection, discoloration, fluid accumulation beneath the skin, numbness and scarring.
In an effort to avoid uneven skin surface and achieve proportional body shaping it would be advantageous to accurately measure the adipose tissue thickness before, during and after a liposuction or other soft-tissue plastic surgical procedure. This would aid in maintaining consistency in the areas in which the liposculpture is being preformed.
It is difficult to directly and accurately measure objects that include layers of different compositions (e.g., skin, muscle and bone). With regard to measuring body adipose tissue layers, skin calipers can be used. A measurement is taken by an operator pinching a subject""s skin and measuring the thickness of the skin fold with the calipers. Various equations are used to predict body density and the percent of body adipose tissue (American College of Sports Medicine (ACSM) xe2x80x9cGuidelines For Exercise Testing And Prescriptionxe2x80x9d, 53-63 (1995)). However, there are many drawbacks to this form of adipose tissue measurement. These measurements are heavily dependent on the operator, and errors and variations frequently occur. Skin fold calipers can only provide an estimate of tissue thickness and are not particularly useful for liposuction procedures.
Another means of determining body density and estimating percent body adipose tissue is a generalized measurement hydrostatic weighing. Hydrostatic weighing requires the subject to be completely immersed in water. This method of measurement could only be employed before and after a liposuction procedure, which would be impractical and costly when the goal is to monitor adipose tissue changes during the surgery. Additionally, the surgeon performing liposculpture and most surgical contouring procedures requires localized measurements. Maintenance of a sterile field is problematic with such a method.
It becomes apparent that a method and apparatus is needed to efficiently and accurately measure adipose tissue before, during, and after a liposuction or soft-tissue plastic surgery procedure. U.S. Pat. No. 5,941,825 dated October 1996 by Lang et al., recognized that ultrasound could be utilized to conveniently and cost effectively measure layer thickness in an object The present invention introduces the use of ultrasound in a hand held device to measure fat tissue thickness in a human. WO 99/65395 dated December 1999 by Lang et al., builds on the previously referenced patent by using anatomical landmarks to measure changes in body adipose tissue. The aim of these two patents is to measure adipose tissue changes over time as a result of diet and exercise.
There is a need for an accurate, convenient, cost effective means and apparatus to measure adipose tissue thickness before, during and after a liposuction or soft-tissue plastic surgical procedure that would provide a high probability of success without producing undesirable side effects yet be conveniently kept sterile when necessary. In addition, a simple device to accurately measure localized body tissue layer thickness could be useful to monitor and map the local or regional effects of dietary changes and diet. The present invention fulfills this need, and further provides related advantages.
It is an object of the present invention is to provide a system for accurately measuring tissue layer thickness before, during and after a liposuction or soft-tissue plastic surgical procedure.
Another object of the present invention is to provide a system to easily create body maps of tissue layer thickness to monitor the effects of exercise or diet.
These and other objects will be apparent to those skilled in the art based on the teachings herein.
In particular, the system can be used to produce a map of the fat (or adipose) or soft tissue thickness at key anatomical points. These measurements can be monitored and compared during a liposuction procedure to guide the surgeon. In one embodiment, the device comprises a remote control and data processing unit, a handheld ultrasound transducer, a monitor to display the information to the user and means to mark anatomical points of interest.
In normal use, the user would mark key anatomical points at the beginning of the procedure. The points could be marked and coded directly on the skin with a water resistant marking pen. In this mode of operation, the point of measurement would be noted by the user and input into the control system. Alternatively, key anatomical points could be marked by placing a series of encoded stickers or stamps. The stickers could be numerically labeled, color-coded or electrically coded. If coded, sensors in the handheld transducer could automatically detect the sticker code and record the location of the measurement automatically. Another technique for registering the measurement points is to use a tracking mechanism similar to that used in electronic track balls or computer mice. In this technique, the user moves the device along a predefined or marked track on the skin that is recorded by the control tunit. The control unit generates a map and records the location of each point of measurement.
The handheld ultrasound transducer uses a single or a plurality of ultrasound generating and detection elements to obtain an effective A-Scan (xe2x80x9cUltrasound in Medicinexe2x80x9d Ed. F. A. Duck, A. C. Baker, H. C. Starritt (1997)) of the tissue structure directly below the transducer. The A-scan will show strong reflections at the interface between the various layers i.e., skin, fat, muscle and bone. Strong ultrasound reflections occur at the interfaces due to impedance mismatch between the various materials. The A-scan signal can be analyzed by the control unit to determine the thickness of the various tissue layers (skin, fat, muscle). During and immediately after the procedure the fat layer may have a mixture of loose fat and water. The reflected ultrasound signal in this non-homogeneous layer will be different than the normal fat layer. Analysis of the reflected signal amplitude in this layer can be used to calculate an effective fat layer thickness. In addition, the ultrasound transducer can operate at two or more frequencies. Since the scattered signal scales strongly with the ultrasound wavelength the ratio of scattered signal at different frequencies can be used to estimate the water-fat mixture.
In one embodiment, the transducer is not connected by a wire or cable to the control unit The transducer and control unit communicate through a wireless means (e.g., RF communication). The advantage of this is that the control unit and display can be far away from the sterile surgical field. RF communication eliminates having to cover the control unit and cable with sterile bags. In addition, in this embodiment the ultrasound transducer is powered by batteries, which reduce the electrical hazard concern.
The remote control unit acquires the data from the handheld transducer and analyzes the data to produce a table of tissue thickness parameters for all the anatomical points. This data can be displayed in a tabulated list or a color-coded anatomical map that can be easily interpreted by the surgeon. Additionally, the display can show the change in the fat layer thickness during the course of the liposuction procedure. The user can control the display and function of the control unit through a keyboard/mouse interface or touch screen.
Using this system, the surgeon will be more able to accurately control liposuction surgery. This will improve procedure outcome by reducing the chances of producing non-symmetric results.
In addition, to being used in liposuction surgery, the present invention can be used to easily create maps of tissue layer thickness. This can be used to monitor changes in fat layer thickness as a function of dietary changes or exercise.
Other objects and advantages of the present invention will become apparent from the following description and accompanying drawings.